Hybrid embryos: UK team plans stem cell first

British scientists plan to create the world's first human stem cells from embryos that are part human and part animal, after the government's fertility watchdog approved the research.

The team at Warwick Medical School hope to use the stem cells to study fatal heart diseases, after being granted a year-long licence for the controversial work by the Human Fertilisation and Embryology Authority.

The researchers, led by Justin St John, will fuse human skin cells with empty pig eggs to create embryos that contain 99.9% human DNA and 0.1% pig DNA. Stem cells extracted from the embryos will then be treated with chemicals to destroy the pig DNA, before they are grown into human heart cells. The animal DNA is destroyed to make the cells behave more like human cells.

If the technique works, it will represent a landmark in stem-cell science and give researchers a way to make almost unlimited stocks of human embryonic stem cells, which in principle can grow into any tissue in the body. Scientists have so far been unable to create stem cells using human eggs, which are in short supply.

Although the stem cells will not contain any animal DNA, they will not be suitable for treating humans directly. Instead, the scientists will use the cells to learn how genetic mutations cause heart cells to malfunction and ultimately cause life-threatening cardiomyopathy.

"Ultimately they will help us understand where some of the problems associated with these diseases arise, and they could also provide models for the pharmaceutical industry to test new drugs," St John says. "We will effectively be creating and studying these diseases in a dish, but it's important to say that we're at the very early stages of this research and it will take a considerable amount of time."

Two other British teams have already been granted licences to create hybrid embryos, but neither hoped to make stem cells that were free of animal DNA.